Reversible propeller



De. 7, 1937. v s. M. F. ENGDAHL 2,101,535

REVERS IBLE PROPELLER Filed July ll, 1956 799.3. Z f3 3f 2) 3; 2) 3) SeHn Mau YH?. Irma@ Engd cxhl NVENTOQ u ATTN.

Patented Dec. 7, 1937 ATI-:NT

REVERSIBLE PROPELLER Seth Maurits Fingal Engdahl, Stockholm, Sweden Application July 1l, 1936, Serial No. 90,117 In Sweden July l2, i935 4 Claims.

The present invention relates to a reversible propeller, especially a propeller fan, the vanes or blades of which have the profile of an Yaeroplane wing.

By giving the blades of such propellerssuitable profiles and shapes with different blade angles, it is possible to reach extraordinarily high effects, when the propellers work in the right direction. In certain cases, as for instance in drying plants, ventilation plants and the like, propeller work is required in various directions and, in such cases the common propellers, having blades shaped as aeroplane wings are not suitable, since they give' a very high effect in one direction, Whereas they are characterized by a very low effect and capacity in the other direction.

Lately, the need of reversible propellers has increased and such propellers have been constructed in many different ways. Propellers of the kind provided with uniform blade profiles have proved to have a bad effect. In order to in` crease the eiect at reversed direction of rotation theV blades, which are in the shape of aeroplane wings, have been provided with an upwardly bent rear edge. It has also been proposed to mount the propellers so that they can swing half a turn in order to obtain just as good an effect in both directions. Further, propellers have been provided with blades adapted to be turned half a turn. However, hitherto there has been no successful arrangement in which a simple construction is provided which is adapted to its purpose and having a good effect in both directions of rotation.

The propeller forming the object of the present invention possesses considerable advantages over prior constructions; it functions with about the same capacity and with a good effect in both directions and is of a very simple construction and may be regarded as a combination of two propellers turned against each other and combined to a unit.

A reversible propeller according to the present invention having vanes or blades whose profile is transversely tapered is characterized in that the vanes or blades are divided into two groups, each group having the same or approximately the same number of vanes or blades which are uniformly spaced on the periphery of the hub, one group of blades having the tapered edge turned in the opposite direction to the tapered edge of the other group, the blades being located beside each other, when seen in peripherie direction, so that one group of vanes Work with high effect at rotation (C1. Uit-159) in one direction and the other group with a high effect at rotation in the opposite direction.

Preferably the vanes or blades of the two groups have both a profile similar to that of an aeroplane wing and exactly the same shape but are 5 turned in opposite directions, whilst in an arbitrary cylindrical cross section the centres of the section areas of the vanes or blades are located on one and the same circle.

An embodiment of a propeller according tc 10 the invention is illustrated in the accompanying drawing.

Figure l shows the propeller in front view, and

Figure 2 is a side view of the propeller.

Figure 3 shows the system of blades, when 1U spread, from which it will be seen that some blades are turned to the right and some are turned to the left, so as to enable part of the blades to work with a high eiect in one direction and the other part of the blades with a good elect in the opposite direction.

Figure 4 shows a device for turnably and lockably mounting blades in the hub of the propeller, when using loose blades.

Referring to the drawing numeral I indicates? the hubof the propeller. One groupof blades are indicated by 2 and the other group by 3.

In the embodiment shown the blades alternate in such a manner that each second blade belongs to one group and the remaining blades to the 30 other group. The blades of the two groups have exactly the same shape but are turned in opposite directions. The blades are secured to one and the same hub and located in one and the r same plane, which is perpendicular to the axis of 30 rotation.

A propeller according to the invention may, however, be embodied in another manner than the one shown in the drawing. The propeller need not be made as a unit, but may be made in two or more parts; the blades of each group may be secured to a special hub or the like, the two hubs with appertaining blade rims being combined to an aggregate. i

If desired, the blades of one group may be shaped or arranged in another manner than the blades of the other group, so that the effect or emciency is higher at rotation in one direction than at rotation in the opposite direction, without abandonment of the essential feature of the invention, viz. an effect that is just as good in both cases.

The blades of the two groups may be located relatively to each other in another manner than alternatingly, and it is not necessary that there is the same number of blades in the two groups.

As shown in the drawing, a suitable manner of embodying a propeller according to the invention is to use for both of the groups of blades identically equal loose blades, which are secured in different positions to the hub. In accordance with the arrangement shown in Figuree, each blade is preferably provided with a pinV Vil, which is rotatably mounted in a slit provided in the hub, by which locking in a certain position is eiected by tightening a screw bolt 5, which extends through a disc 6 into a threaded hole of the pin 4. The blades of the various groups are locked in a position, where the blades of one group are turned half a turn in relation to the blades of the other group.

Propellers according to the invention are specially adapted to be used as propeller fans but they may be advantageously used also for other purposes.

The advantage of a reversible propeller in accordance with the invention does not lie only therein that a good effect or eiiiciency is obtained in both directions but also therein that a uniform utilization of the supplied effect is obtained.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A reversible screw propeller of the character described, comprising a hub and a plurality of blades, each blade having a transversely tapered profile, the blades being arranged in two groups, each group having its blades uniformly spaced and disposed with their tapered edges turned in a direction opposite to the tapered edges of the other group, in such a manner that rotation of the propeller in one direction will bring one group of blades into eective operation and rotation of the propeller in the opposite direction will bring the other group of blades into effective operation.

2. A reversible screw propeller for fans, comprising a hub and blades having the profile of an areoplane wing, said blades being arranged into two groups, each group consisting of more than two blades and of substantially the same number of blades uniformly spaced about the periphery cf the hub, one group of blades being with their working edges turned in the direction opposite to the working edges of the blades of the other group, the blades of one group alternating with the blades of the other group about the hub, in such a manner that one group of blades works with high effect during rotation of the propeller in one direction and the other group of blades works with high effect during rotation of the propeller inthe opposite direction.

3. A propeller, as claimed in claim 2, in which the blades of the two groups are identical in shape, and disposed about the hub one behind the other.

4. A propeller, as claimed in claim 2, in which axes of the blades are disposed on the same plane formed by a substantially transverse section through the hub.

VSETI-I MAURITZ FINGAL ENGDAHL. 

